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Overview

Natural disasters destroy more property and kill more people with each passing year. Volcanic eruptions, earthquakes, hurricanes, tsunamis, floods, landslides, fires and other natural events are becoming more frequent and their consequences more devastating. Del Moral and Walker provide a comprehensive summary of the diverse ways in which natural disasters disrupt humanity and how humans cope. Burgeoning human numbers, shrinking resources and intensification of the consequences of natural disasters have produced a crisis of unparalleled proportions. Through this detailed study, the authors provide a template for improving restoration to show how relatively simple approaches can enhance both human well-being and that of the other species on the planet. This book will appeal to ecologists, land managers as well as anyone curious about the natural world and natural disasters.

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"Restoration biologists and technicians, land managers, and students of these fields would be well served by reading this excellent, concise account of the lessons learned by these two ecologists."
Dan Kunkle, Wildlife Activist

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Meet the Author

Roger del Moral is Professor of Biology at the University of Washington. His research includes the mechanisms of vegetation response to disturbances caused by volcanoes, glaciers, grazing and urbanization. He has practised wetland restoration for over 20 years and has experience with dune and subalpine meadow restoration. He had studied volcanoes on four continents, including detailed studies of Mount St. Helens that started in 1980.

Lawrence R. Walker is Professor of Biology at the University of Nevada Las Vegas. His research focuses on ecological plant succession and the theoretical and practical lessons for restoration. His research in succession and restoration has encompassed work on volcanoes, dunes, glacial moraines, floodplains, landslides, cliffs, hurricanes, reservoir drawdown zones, abandoned roads and mine tailings.

Read an Excerpt

1

Introduction: a crescendo of destruction

1.1 DISTURBANCE AND HUMAN INTERACTIONS

The pristine world of the past was filled with cataclysms. Volcanoes, earthquakes, floods and fires shaped today’s landscapes and every living organism evolved in response to natural disturbance. What we call Nature survived in a finely tuned balancing act between the forces of destruction and recovery. Recovery of Nature after destruction was inevitable, but it occurred at variable rates and with a constantly evolving mix of plants and animals. Occasionally natural disturbances were so violent that many species became extinct. Today, the rules have changed; humans have profoundly altered the balance of destruction and recovery, by intensifying natural disturbances and creating many novel ones, without an equal emphasis on recovery. What are the consequences of this meddling by humans with the future of this planet?

Humans have always been at the mercy of large natural disturbances, though we try to forget this fact. The Minoans left little but legends (e.g. Atlantis) after the massive eruption of Santorini (Thera) in about 1623 BC. Agriculture in Japan suffered terrible blows from sixth century volcanic eruptions, as did the economies of both Iceland and Europe by theeruptions of Laki in 1783. Yet we continue to build on active volcanoes, steep slopes prone to erosion and floodplains subject to flooding. Recently, we have felt a growing, yet false, sense of protection from the natural forces of destruction because many of us now live in safe, artificially created environments. Ironically, this decoupling from reality, combined with our immense population growth, results in three dilemmas.

First, that there are many more humans now than ever before implies greater contact with and greater mortality from the same set of natural disturbances. Dense populations now inhabit clusters of cities

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where volcanoes once spewed ash onto uninhabited lands. Second, our collective “ecological footprint” magnifies the effects of natural disturbances on humans. Tsunamis and hurricanes are more devastating where protective coral reefs and mangrove swamps have been destroyed. Landslides are more frequent where logging or road building destabilizes slopes. Deforestation also intensifies the severity of natural floods, while grazing semi-arid lands fuels the expansion of desert dunes. Finally, humans continue to modify the earth so much that an entirely new set of disturbances threatens. These new effects include pollution, biological invasions (Fig. 1.1), overgrazing (Plate 1) and rapid global climate change. Mining and energy production create toxic landscapes (Fig. 1.2). We have homogenized the world’s fauna and flora and global warming is changing how species are distributed around the world. What was once “background noise” from human activities has become the principal signal, impossible to ignore.

This book describes how we can harness the natural processes of recovery to address some of these dilemmas caused by humans.

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Our challenge is to mitigate the immediate effects of disturbances, then to apply the best knowledge and technology to redress the damage.

There is a synergistic interplay between nature and human actions as humanity expands. The geographic and cultural landscapes of this planet have changed dramatically, altering the interactions among humans and disturbances. As the human population grows, it expands into increasingly fragile environments, intensifying impacts of natural disturbances (Fig. 1.3). With some validity, many natural philosophers speak of the “end of nature”, implying that no place on earth now escapes significant human impacts. Against the background of pervasive human impacts, we believe that our efforts to hasten recovery of landscapes should intensify dramatically.

The barrage of recent natural disasters around the world highlights our vulnerability to the forces of Nature. The Indian Ocean tsunami of December 26, 2004 demonstrated that the 39 percent of us living near coastlines are certainly living in a risky habitat. Those not in coastal areas face other direct hazards (e.g. volcanoes, earthquakes, landslides, fires) and also such indirect impacts as reduced production and shipping of resources from the impacted coastal communities. Damage to one society affects us all in this new era of globalization.

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Further, most of the world’s active volcanoes are near oceans and can cause underwater landslides that can, and have, resulted in catastrophic tsunamis.

The first, and most tragic, loss from any natural disaster is human life (Table 1.1). More people die, unheralded, from natural disasters than from wars. A second loss is that of property, investments and livelihoods. Obvious direct costs spawned by disturbances such as the Bangladesh floods in 1970, or Hurricane Katrina in the USA in 2005, continue to increase, and the costs even to plan for mitigation of the impacts from these events are staggering. Jobs are lost, people are driven from their homes and lives are devastated. The third type of damage incurred is to the structure, efficiency and productivity of natural ecosystems. Although rarely considered, let alone quantified, these losses are also immense. For example, Hurricane Katrina destroyed over 250 km2 of coastal wetlands, about the size of the Cayman Islands. Multiple natural disasters have a cumulative, destructive impact on natural resources that puts us all at risk. Human activities exacerbate natural disturbances and create novel ones on increasingly large scales. For example, fires and logging destroy several hundred thousand square kilometers of forest per year, an amount of carbon equal to two-thirds of the total carbon emitted by burning fossil fuels. In Europe, 8,000 km2 of forest (an area the size of Cyprus) per year burns, and the size, number and intensity of wildfires is increasing. We face a true crescendo of destruction of our own making.

Table 1.1.Major natural disturbances in human history. The devastation from volcanoes may be direct or indirect from climatic effects or tsunamis. Earthquakes directly destroy cities, but they may also generate powerful tsunamis, or create huge landslides. Dates are AD except where otherwise noted.

10,000 killed; ash cloud cools planet leading to further 100,000 deaths from famine and disease

1902

Mount Pelée (Martinique)

30,000 killed by pyroclastic flows

Earthquakes

526

Antioch (Turkey)

75,000 killed; weakens Christianity in east

856

Corinth (Greece)

45,000 killed; city abandoned

1556

Shanzi Province (China)

800,000 killed directly; huge toll from landslides

1755

Lisbon (Portugal), followed by tsunamis that devastate coastal regions

100,000 killed; Portuguese influence plummets

1923

Kanto Plains (Japan)

150,000 killed; modern Tokyo reconstructed

2003

Bam (Iran)

23,000 killed in poorly built houses

2005

Mountainous Pakistan

80,000 crushed in building collapses and landslides

Tsunamis

1623 BC

Collapse of Thera caldera causes 150 m tall tsunami

Huge toll; Minoan culture devastated

1531

Earthquake triggered; Lisbon (Portugal)

70,000 killed (30,000 in earthquake)

1883

Collapse of Krakatau cone (Indonesia)

37,000 killed; some climate effects

2004

Indian Ocean 9.3 earthquake

300,000 killed; many communities destroyed

Landslides

1966

Mine waste heap collapses at Aberfan (Wales)

144 people killed

1998

Hurricane Mitch (Honduras)

18,000 people killed (from all impacts)

Floods

1931

Yellow River (China)

3.7 million people killed; weakened resistance to invasion by Japan

Fires

64

Two-thirds of Rome burned

Death toll limited; Christians blamed for destruction

1666

London

Most of London burned; a true restoration followed

1871

Chicago

300 killed, but this allowed rejuvenation of city

Hurricanes

1274

Sea of Japan

12,000 Mongols killed invading Japan

1281

Sea of Japan

70,000 Mongols killed during second invasion

1780

Lesser Antilles (Martinique, Barbados, St. Eustatius)

20,000 killed

1900

Galveston, Texas

12,000 killed

1970

Bangladesh

500,000 killed by storm surges

1974

Honduras (Hurricane Fifi)

10,000 killed

Disturbances have altered the course of human history in many ways (Table 1.1). In this book, we will focus on how humans respond to and often intensify the effects of large-scale, natural disturbances such as volcanoes, earthquakes, floods and fires. We will also cover some purely anthropogenic disturbances, such as grazing and mining, that impact landscapes on a large scale. However, we will not discuss natural and human generated disturbances that do little damage to landscapes, even if their impact on humans is enormous (e.g. urban fires, epidemics and famine). We will say little about deliberate destruction, usually associated with warfare. Examples include the massacres that followed the capture of such cities as Milan (by Goths in AD 538), Jerusalem (by Christians in 1099) and Nanking (by Japanese in 1937–8). The “normal” business of military activity, however, is included. For example, driving heavy vehicles across the landscape destroys vegetation which should be restored.

Disturbances are not all traumatic exclamation points. Many result when the natural ability of an ecosystem to withstand chronic adverse effects and yet remain productive is finally overwhelmed. Many systems will not be able to recover from certain disturbances even when the disturbance ceases. Deforestation and overgrazing are well-known causes of gradual yet severe disturbance. Both processes promote erosion and nutrient losses. Others, less widely appreciated, include accumulating pollutants, siltation of marshes, the gradual desiccation of lakes due to plunging water tables and the filling in of wetlands. We will explore these slowly unfolding disturbances in several places.

We will also describe a few devastating forces from the perspective of how ecosystems respond. In particular, lakes and coastal ecosystems are being subjected to natural disasters, such as hurricanes, and human behaviors that destroy marshes and lakes. As the sole species that is a global geological force, we must accept the duty of stewardship. It has been rare for a society to understand the consequences of chronic disturbances and rarer still for effective policies to be instituted to avert crises. Forces that a healthy society could withstand can destroy a weakened one. To guard against adverse impacts of changing climates and other insidious disturbances such as soil erosion and desertification, ecosystem damage should be avoided and repaired to retain productivity and resilience. Morality aside, it is in our own best interests that we mitigate the effects of both self-imposed and natural disturbances.

Ecology has emerged from the academies to become a discipline that is inextricably tied to the fate of humanity. Concepts such as sustainability and biodiversity are now widely discussed and ecological journals that deal with practical applications are common. Restoration has joined conservation as a scion of ecology. While ecologists know a lot about restoring land, much remains to be learned and translated into action. As is always true, the ability to act has to be combined with the will to act. The will of a society can only be derived from a political and economic calculation that demonstrates that action is more valuable than inaction. We believe that the political will for a broad and comprehensive approach to landscape rehabilitation does not yet exist. While the final reports of endless international conferences are filled with action plans to improve the land, those plans

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are rarely implemented. We will demonstrate that restoration is a necessary, though far from sufficient, action to sustain societies, mitigate foreseeable disturbances and provide opportunities for greater human well-being. Today, we can make choices. Informed choices enhance the productivity of ecosystems and promote the stability of a society. As Jared Diamond convincingly demonstrates in “Collapse,” the wrong choices have led many civilizations to fail. The Babylonians, Mayans and the Anasazi (Fig. 1.4) were three advanced groups that disappeared or became ghosts of their former glory due largely to disturbances after long-term environmental degradation. Many cultures rose and fell due to low-grade disturbances such as overgrazing or poor agricultural practices that caused salinization and erosion. Rarely were signs of gradual decline noted until some extreme event triggered the crash of the economic basis for the culture in question.

Security can ultimately be defined in ecological terms, and restoring ecosystems to productivity and health is fundamental to the security of any society. In these terms, human societies are less secure now than at any time since the expansion of agriculture. Various threats exist, not only to particular countries or regions, but also to the globe and to all its inhabitants. The environment, and the magnificent biodiversity that it sustains, is gravely threatened. Direct pressures include conversion of habitats (e.g. forests to farms; farms to deserts), invasions of exotic species, over-harvesting of resources and pollution. Indirect pressures include habitat fragmentation and climate change. We will not survive long on this planet without addressing the urgent issues of ecological security and sustainability.

1.2 DISTURBANCE AND RECOVERY

Intense natural disturbances are normal events that can benefit ecosystems. Floods deposit nutrients that in turn support fertile alluvial valleys. Fires rejuvenate soils, help to control diseases and often stimulate new growth. Even volcanoes benefit the landscape by creating fertile land. Indonesia and Sicily, two densely populated regions in the world, were formed by volcanism and their soils retain their fertility even under intensive agriculture. Such disturbances as floods, fires and volcanoes thus initiate cycles of renewal without which the landscape would otherwise degenerate, as nutrients are lost. Very old soils such as are found in Australia and Africa are relatively infertile. The new surfaces that result from disturbance are often more fertile than the surfaces they cover or remove. Under natural conditions, biological colonization and physical weathering repair the devastation spawned by natural disturbances through the process of natural recovery or ecological succession.

The key to being able to meet the challenges posed by natural disturbances is an understanding of succession. Ecological succession describes how ecosystems repair themselves after disturbances. Ecologists are developing a deeper understanding of these processes and have learned many of the constraints on natural succession. We can use these lessons to accelerate and improve restoration efforts on devastated land and to improve the economic efficiency of these efforts (Fig. 1.5).

Natural recovery may resurrect an ecosystem if disturbance is within historical bounds. Primary succession is one of the most important ecological processes on the planet (Box 1.1). It results when the biota reclaim newly formed land, often against severe odds. Among the constraints to succession are combinations of infertility, lack of suitable germination sites, lack of soil, drought and the failure of colonists to reach the site. Secondary succession is the recovery from less

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profound disturbances that allow at least some survivors to reestablish. It is more rapid and less constrained than is primary succession.

Where human impacts are limited, succession can produce intact, fully functional ecosystems, even if they are composed of arrays of species that differ from the pre-disturbance collection. In the contemporary context, where barriers to dispersal and migration abound and where even the air is sometimes toxic, natural recovery is problematic. Normally, renewal includes weathering, nutrient inputs, colonization and habitat improvements both by the colonizing species and others. Today, it is unlikely that unaided recovery can produce natural landscapes. Agriculture arrests succession at a young stage so that, when the land is abandoned, it may not recover. Forestry deflects succession to more economically productive but biologically impoverished habitats such as tree farms. When forestry ceases, many integral species may not be available in order for succession to proceed unaided.

Humans interact with the disturbance regime of any region by mimicking natural effects (e.g. pavement resembles lava) and altering the frequency (e.g. by fire prevention, flood control) or intensity (e.g. by adjusting grazing levels) of a disturbance. Humans also create unprecedented disturbances of many types (e.g. mine tailings, acid deposition). These alterations make it increasingly unlikely that natural succession can restore damaged landscapes without help.

Box 1.1 How natural systems recover from complete devastation

Primary succession is the process of ecosystem development on barren surfaces where severe disturbances have removed all life. It requires establishment of a biota adapted to harsh conditions. As physical and biological forces ameliorate conditions, new species arrive, while some pioneers are excluded. Complex systems eventually develop from simple components. The process is influenced by local conditions, context and site history.

All new surfaces are initially devoid of life, so primary succession has been crucial throughout earth’s history. Today, all communities of plants, animals and soils are the result of primary succession. It is this process of recovery of ecosystems after disturbance that provides the clean air and water and fertile soils that humans and all organisms need to survive.

When organisms survive the disaster, recovery is called secondary succession. Secondary succession is less dependent on the vagaries of dispersal and is therefore more predictable than primary succession. However, secondary succession in one place can follow several alternative trajectories that depend on chance factors.

Ecologists distinguish autogenic succession, when the mechanisms that drive species change are derived from the organisms within the community (e.g. competition; herbivory) from allogenic succession, when external forces determine species change (e.g. sediment transport from a flood). Change in the early stages of primary succession is due mostly to allogenic mechanisms, but autogenic mechanisms become more important as primary succession proceeds or during secondary succession. Categories such as primary, secondary, autogenic and allogenic denote arbitrary points along environmental gradients and are not easily distinguished.

1.3 THE FUTURE IS NOW, TIME IS SHORT

Planning and foresight are the keys to long-term survival of modern civilization, yet neither as individuals nor as societies do we plan for the truly worst case. We seem to hope for the best and plan accordingly. We somehow believe that whatever our situation, we are protected from the disasters of the past or accidents in the future. We appear incapable of learning the simple lesson that survival depends on the health of local ecosystems, and that we must nurture these systems. Floods, droughts, volcanoes and earthquakes routinely tip the balance toward chaos. As should by now be clear, there is nothing in our political, social or economic systems that renders our societies immune from the forces of nature. The rules about how resources and disturbances affect civilizations are universal, and a central force in the decline of empires seems to have been a failure to respond effectively to environmental disturbances.

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